Supermarkets are responsible for a huge chunk of newspapers' advertising income, but is consumer advertiser enthusiasm for print a ticking timebomb for newspapers?

Between them, the eight biggest UK supermarkets spent £186.6 million on advertising with UK newspapers in the last year, according to Nielsen (via Newsworks). That's almost one quarter of the newspaper adspend from the UK's top 100 advertisers.

But despite the explosion in digital audiences for newspaper publishers, with the main publishers reaching close to or in excess of 100 million visitors a month, in aggregate those supermarkets put just 3.2 percent of their advertising budgets into digital newspaper products.

So with a total combined pot of advertising of more than £500 million, the top eight supermarkets spend £180 million on print advertising and £6.1 million on digital newspapers.

There is variation here. Marks & Spencer spends 21 percent of its newspaper budget online - equivalent to £4.4 million. But excluding M&S, the remaining seven supermarkets spend just over 1 percent of their spend with newspapers online.

Across the board, the average proportion of newspaper digital spend by the top 100 UK advertisers on digital is 5.2 percent. That's still not huge, but a firmer endorsement of digital than from supermarkets.

Supermarkets are enthusiastic supporters of newspapers but they are overwhelmingly putting their money into print ads, not digital.

Recent reports of Tesco's reluctance to advertise on The Sun website once it goes behind a paywall next month could signal that with access models changing, big retailers may be even less keen to shift spend to digital.

Shifting platforms

We shouldn't be in any doubt how crucial big retailers are to the media economy. Compared to other big ad spenders, supermarkets are spending more than twice as much on newspapers.

An average of 36 percent of their ad budgets go to newspapers, compared to an average of 16.2 percent across the UK's top 100 advertisers.

If big retailers haven't begun embracing digital advertising with new brands now, you have to ask if they ever will. Could spending move over to rivals such as Facebook, or will Tesco simply use its own growing media empire to reach consumers directly?

The odds of this relationship surviving the transition to digital unscathed look slim.